1. Field of the Invention
The present invention relates to mechanization and automation of production processes. More particularly, the invention relates to apparatus for thickness sorting of sheet material.
The apparatus of the invention is suitable for sorting furs according to the thickness of the leather, before the furs are dressed.
2. Description of the Prior Art
Known apparatus for thickness sorting of a sheet material comprises a belt conveyor for transport of sheet material to accumulating hoppers having distributing plates. The drivers of the distributing plates are electrically connected, via a control unit, to an output of an assembly for measuring the material thickness (cf. USSR Inventor's Certificate No. 103,127, Int.Cl.B07).
The control unit of the known apparatus comprises a reference voltage source and a signal comparison unit in which the signals obtainable from the thickness measuring assembly are compared with reference voltage signals.
The thickness measuring assembly may be implemented, for example, as a radioisotope thickness gauge which comprises a radioactive source and a radiation detector which senses the radiation passing through the material under measurement (cf. Great Britain Patent No. 1,058,583, Int.Cl.G1A).
However, the known apparatus cannot adequately handle sheet materials on which wrinkles are likely to form. This applies, for example, to furs. If there is a wrinkle at a point of measurement, the measurement result is erroneously high and results in improper sorting.
In the known apparatus, the material passes through the measurement area in an untightened or limp condition, and the thickness measuring assembly produces, at the detector output, a signal proportional to a thickness characteristic of a specific point of measurement. It is known, however, that the thickness of the leather of a fur skin changes considerably within a single sample, since dirt and pieces of meat or fat may be encountered. Therefore, with the known apparatus, it is impossible to achieve reliable thickness sorting of a material whose thickness tends to vary along its length.
In addition, the known radioisotope thickness gauge has no zero shift corrector, and therefore should be adjusted by hand, which increases its maintenance requirements.